Capacitor polarity and overvoltage

Question

after watching few videos on YouTube with exploding capacitors i decided to learn few things about the polarity and the voltage rates by trying to make a capacitor explode.

I made few test to try on then. First was the overvoltage test. I took a capacitor rated at 6.3V and i gave him 12V directly from a wall adapter. Nothing* happened however when i pulled it out from the protective box it was verry hot! So i straped a digital thermometer on the capacitorto monitor the temperatures and i put it on with the cables reversed. That was part of the second experiment with the reverse polarity. Quicly the capacitor jumped from the 25C (my room temperature) to 83C and then back down to 27C however no explosion! But after mesuring the capacitance with a multimeter the capacitor was completely dead. I couldn't mesure anything.

After this experiment i have the following questions.

• What are the perfect conditions for a capacitor to explode?
• What killed my capacitors? The extreme temperature, the voltage or the polarity?
• Should i be worried about the polarity of the power on my projects? (Except from ICs)

Few things for the capacitor:

• 100uF
• 6.3V
• -40 to +105 temperature
• Chinese el' cheapo

Answer 1

i would recommend repeating the experiments with fresh (unmolested) caps each time, applying only 1 stress at a time: (a) over-voltage, (b) reverse polarity, what happens when you (a) first then (b), then vice-versa. in your first experiment, the over-voltage may well have been the killer, but reverse-voltage on an electrolytic cap = instant heat death.

there is no perfect conditions to kill a cap, it depends on the type of cap, how long and how high the over-voltage is, what temp it reaches due to the abuse to further damage it, etc.

& as Meletis said, if you really want to see a bang, try some tantalum caps!

but PLEASE, wear protective eye cover when doing these tests, caps WILL explode violently and spray toxic chemicals, &/or molten metals, sometimes at high speed. this experimenting is not worth an eye. and do so with fire extinguishing apparatus handy too (fire blanket, extinguisher (of type apropriate to electric fires)).

your final question, not sure what you're really asking - but polarity is fundamental to electronics.